1. Technical Field
This invention relates generally to monitoring of the aerodynamic performance of aircraft and more particularly to use of thin piezoelectric devices adapted for attachment to exterior surfaces of structures such as aircraft surfaces and in particular aircraft engine inlets, external fuel tanks and airfoils. Such devices are particularly well suited for analyzing activity on the surface which can be used to describe complex boundary layer flow phenomena, vortex flow structures, and warnings of impending stall conditions due to ice accretion or high angle-of-attack. Advantageously, the devices may be employed in the active manipulation of airflow over an airfoil and, more particularly, in the detection and control of boundary layer and vortex flows. Such active control methods may include use of laminar flow control mechanisms (acoustic wave excitation, compliant walls, etc) or active vortex generators. Additionally, the devices may be used to activate deicing systems such as electrothermal heaters to automatically remove ice accretion on aircraft surfaces.
2. Description of the Prior Art
While recently developed flow sensor technologies have made some advances, even the most current systems have shortcomings. They generally require extensive modification of aircraft structure, cannot monitor large areas, cannot provide continuous monitoring, are prone to misinterpretation, cannot be operated in-flight, suffer from inaccuracy, are too complex, bulky and not self-contained, or require extensive power sources. Additionally, known systems are generally very limited in what they measure.
With respect to complex flowfield investigations, measurement techniques which cover the surface as completely as possible (i.e. by employing sensor arrays instead of individual sensors) and monitor a plurality of parameters are clearly desirable. Specific areas which will especially benefit from such a system will be discussed in detail sufficient to enable one to understand the context within which the present invention preferably operates and the problems which must be overcome.